getView方法在GridView中显示文本和图像？

Question

我试图获取文本，从网络服务器JSON图像，并使其在网格视图 从服务器获取数据时，但问题是获取视图

这里只是试图让文本，但它的确定弹出错误的列表中的logcat关于getview方法

logcat的错误：

02-15 20:51:13.628: E/AndroidRuntime(1135): FATAL EXCEPTION: main 
02-15 20:51:13.628: E/AndroidRuntime(1135): java.lang.NullPointerException 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at de.vogella.android.twitter.json.ParseJSON$ImageAdapter.getView(ParseJSON.java:211) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.widget.AbsListView.obtainView(AbsListView.java:1315) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.widget.GridView.onMeasure(GridView.java:932) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.view.View.measure(View.java:8171) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:381) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:304) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.view.View.measure(View.java:8171) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.view.View.measure(View.java:8171) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:526) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:304) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.view.View.measure(View.java:8171) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:245) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.view.View.measure(View.java:8171) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.view.ViewRoot.performTraversals(ViewRoot.java:801) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.view.ViewRoot.handleMessage(ViewRoot.java:1727) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.os.Handler.dispatchMessage(Handler.java:99) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.os.Looper.loop(Looper.java:123) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at android.app.ActivityThread.main(ActivityThread.java:4627) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at java.lang.reflect.Method.invokeNative(Native Method) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at java.lang.reflect.Method.invoke(Method.java:521) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626) 
02-15 20:51:13.628: E/AndroidRuntime(1135):  at dalvik.system.NativeStart.main(Native Method) 

代码：

public class ParseJSON extends Activity { 
GridView MyGrid; 
Bitmap bmImg; 
ImageView imView; 

/** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

     MyGrid = (GridView)findViewById(R.id.grid); 
     MyGrid.setAdapter(new ImageAdapter(this)); 

    } 

    public class ImageAdapter extends BaseAdapter { 
     private Context mContext; 

     public ImageAdapter(Context c) { 
      mContext = c; 
     } 


     public String readTwitterFeed() { 
      StringBuilder builder = new StringBuilder(); 
      HttpClient client = new DefaultHttpClient(); 
      HttpGet httpGet = new HttpGet(
        "http://www.zigwheels.com/api/zigtvApi.php?method=data&module=News&section=News"); 
      try { 
       HttpResponse response = client.execute(httpGet); 
       StatusLine statusLine = response.getStatusLine(); 
       int statusCode = statusLine.getStatusCode(); 
       if (statusCode == 200) { 
        HttpEntity entity = response.getEntity(); 
        InputStream content = entity.getContent(); 
        BufferedReader reader = new BufferedReader(
          new InputStreamReader(content)); 
        String line; 
        while ((line = reader.readLine()) != null) { 
         builder.append(line); 
        } 
       } else { 
        Log.e(ParseJSON.class.toString(), "Failed to download file"); 
       } 
      } catch (ClientProtocolException e) { 
       e.printStackTrace(); 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 
      return builder.toString(); 
     } 


     public int getCount() { 
      return 10; 
     } 

     public Object getItem(int position) { 
      return null; 
     } 

     public long getItemId(int position) { 
      return 0; 
     } 

     // create a new ImageView for each item referenced by the Adapter 
     public View getView(int position, View convertView, ViewGroup parent) { 
      View MyView = convertView; 


      if (convertView == null) { // if it's not recycled, initialize some attributes 
       LayoutInflater li = getLayoutInflater(); 
       MyView = li.inflate(R.layout.main, null); 



      } 
      TextView tv = (TextView)MyView.findViewById(R.id.grid_item_text); 







      try{ 
       JSONArray jsonArray = new JSONArray(readTwitterFeed()); 

       String[] values = new String[jsonArray.length()] ; 


       for (int i = 0; i < jsonArray.length(); i++) { 

        JSONObject jsonObject = jsonArray.getJSONObject(i); 

        jsonObject = jsonArray.getJSONObject(i); 
        if(position < values.length){ 
        values[i] =jsonObject.getString("headline"); 

        tv.setText(""+ values[position]); 
        } 




       }}catch(JSONException e){ 

        e.printStackTrace(); 

       } 





      return MyView; 
     } 



} 
























} 

Answer 1

如果你的position变量大于当前的i，那么你会得到一个NullPointerException，因为你没有值[位置]（这是因为你在每次调用getView（）时重置values数组）。

尝试像

for (int i = 0; i < jsonArray.length(); i++) { 

       JSONObject jsonObject = jsonArray.getJSONObject(i); 

       jsonObject = jsonArray.getJSONObject(i); 

       values[i] =jsonObject.getString("headline"); 
       if(position < values.length) 
        tv.setText(""+ values[position]); 

       // thumbnail[i] =jsonObject.getString("thumbnail"); 

      }